Few can be in any doubt that parliamentary demo­cracy is facing a huge chal­lenge. The facts are that some MPs have abused our allowances for second homes. The system has clearly not met the basic tests of credibility and transparency.

We have reached a defining moment – for the public, politicians and, yes, the media. We need a three Rs approach: reparation, reassurance and renewal. On expenses, we must make reparations with a system of reassessment and payback. We have to provide reassurance immediately with an interim system imposing moratoriums on claims for furniture and a cap on interest claims. And, for the future allowance system, we need the independent input that the Committee on Standards in Public Life will provide. But we also must seize the opportunity for much wider debate and action to address the underlying problems – and to renew politics and parliament.

No one is arguing for the status quo, and there is a fresh chance for progress. That will be a debate that takes place within all the parties. As leader of the House of Commons, I believe that it needs to reach all sides of the house – and involve those outside the house too.

And, though I know it is hard to get a hearing on it now, I will continue to argue what I believe to be the truth. That most MPs go into parliament as a matter of public service, and are hard-working, decent and honest. These MPs are every bit as angry as the public to learn not only that public money has been misused, but that their own reputation and that of parliament has been stained in the process.

Public anger and rejection of politicians is of such great concern because politics matters. At a time of the global financial crisis, when people's jobs and homes and businesses are threatened, they need a political system they can trust. The bigger the scale of action that government has to take, the greater the need for strong, deeply rooted legitimacy. That legitimacy is weakened when the institution of parliament becomes undermined. It is often said that government needs strong opposition. I think government needs a strong parliament. And, over the last week, parliament's reputation has taken a hammer blow.

Even before the revelations, the house had acted. We agreed last year that MPs should no longer vote on their own pay. We voted to clarify and tighten the allowance system. We've voted to end the second home allowance for outer London MPs. We have already endorsed the inquiry by the Committee on Standards in Public Life and asked it to recommend changes as soon as ­possible. And we all agree that we need to go beyond parliament in our search for a solution. There is more the parties agree on than divides us.

We all agree that there should be integrity and high standards. We all agree that the MPs' constituency link is vital. We agree that you should not need independent wealth to serve in parliament – what Americans call the "log cabin to White House" principle. And I hope that we will all agree that our work as MPs should be our single focus and that we should not have outside jobs.

As leader of the house, I shall ­continue to argue for a cross-party approach. The last thing that a public appalled about abuse of public money wants to see is the unedifying spectacle of parties turning it into a political competition. The committee on members allowances is cross-party.

That is not to argue for an end to political debate and replace it with a soggy consensus. Parliament and politics are important precisely because there are deeply held, different views about public policy and big choices. But there is a consensus about the need to sort out our expenses – and we will.